Information recording devices have been conventionally known which magnetically, optically or magneto-optically record information on information recording media and which may be represented by hard disk drives (HDDs). The hard disk drives magnetically record information on magnetic disks, which comprise recording layers formed on substrates, by means of magnetic heads. Known substrates generally include aluminum substrates and glass substrates, among which glass substrates have been increasingly used for applications for which a growing need for strength and reliability is felt such as laptops, on-vehicle devices, game machines etc. because glass substrates have high surface hardness, superior surface smoothness and less defects on surfaces. In hard disk drives, a magnetic head floats relative to a magnetic disk to write information on the magnetic disk. Recently, in order to improve recording density, reduction in flying height of magnetic heads is required.
In order to address this need, the dynamic flying height (DFH) control technique has recently been studied and developed in which, upon reading/writing information from/on an information recording medium, the distance between the so-called air bearing surface (ABS) and the information recording medium is reduced by bringing only a head element which is responsible for reading and writing in a magnetic head close to the information recording medium, and this technique is disclosed, for example, in Patent Document 1 and Non-Patent Document 1. In the DFH control techniques disclosed in Patent Document 1 and Non-Patent Document 1, the distance between a magnetic head and a magnetic disk is reduced by, upon reading/writing information from/on the magnetic disk, supplying electric power to a heater incorporated in the magnetic head to raise an ABS of the magnetic head opposing to the magnetic disk.    Patent Document 1: Japanese Patent Application Laid-open No. 2008-198307    Non-Patent Document 1: “Magnetic Head Slider Flying Height Control Technique by Micro Thermal Actuator and Its Progress”, Journal of the Japan Society of Mechanical Engineers, June 2008, vol. 111, No. 1075, p. 541